It is the purpose of the proposed research to develop and test specific hypotheses regarding the central control of desynchronized sleep (D) at the level of single neurons by the method of chronic extracellular microelectrode recording. Results in hand indicate that the giant neurons of the cat pontine tegmentum (FTG), a region whose intrinsic anatomy and experimental destruction had suggested a role in D sleep, satisfy better than other cell groups three physiological criteria of a central control system: (1) greater selectivity of discharge during D; (2) earlier anticipatory tonic rate change in transition to D; and (3) earlier anticipatory phasic rate change in association with the eye movements of D. Long-term recordings show FTG neuronal activity to be (1) consistently selective across repeated D cycles; (2) stereotyped, for each cell, within each cycle; and, (3) periodic when a series of cycles is considered. We have recently discovered that other cells, in the region of the locus coeruleus, fire in a tonically reciprocal fashion with respect to the FTG. All of these findings together suggest that FTG neurons function as output elements in an oscillatory brain stem system during D sleep. We plan to extend these findings and to test their implications in several new ways. First, we propose to define more precisely the axonal domain of the FTG by anatomical and physiological techniques. Second, we propose to make simultaneous recordings from two or more individual neurons within and across the cell fields that we presume to be interacting. Third, we propose to combine lesion and stimulation techniques with extra-cellular unit recording to clarify the nature of the interaction between elements in the control system.